Aluminum bearer for a bearer joint in a vehicle body work and method of replacement

ABSTRACT

A bearer joint for a vehicle bodywork, and in particular a longitudinal front bearer joint, and a process for placing an aluminum bearer on the bearer joint in the vehicle bodywork. The bearer joint comprises a cast aluminum connector for joining together a first forward bearer and a second adjacent bearer. The connector includes a tubular aluminum recess for receiving the rearward end of the first aluminum bearer which is fixed thereto by a transverse weld seam at the front receiving edge of the recess. To replace a damaged front bearer, a ring cut is made to the outer wall of the aluminum recess at a distance from the forward receiving edge corresponding to the zone of thermal influence of the heat affected zone adjacent the weld. A damaged front bearer is then withdrawn from the recess and replaced by a new front bearer which is also welded to the new forward cut edge of the aluminum recess. In this way the front bearer is replaced without compromising the original strength of the bearer joint. The depth of the aluminum recess is sufficiently deep to permit a desired number of repetitions of the repair procedure and still provide for a sufficient depth to ensure a positive locking engagement of the front bearer within the recess.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to repair techniques for a motorvehicle bodywork. More particularly, the invention relates to a methodor apparatus for replacement of an aluminum bearer at a longitudinalbearer joint in a vehicle bodywork.

2. Description of the Prior Art

From published European Patent document EP-PS 0 146 716, it is known howto produce the load-bearing structure of a vehicle bodywork by usingnodal connector elements for joining together hollow section bearers.Extruded aluminum sections are used as the hollow section bearers andcast aluminum joint pieces are used as the nodal connector elements.

In the familiar longitudinal bearer design of a vehicle frame disclosedin German Patent document DE-OS 37 40 402, the longitudinal bearers arepartitioned before the assembly is suspended in place. Here again, theforward most portion of the longitudinal bearer is fashioned as aplurality of joined together deformation elements, so that they are moreeasily deformed than the adjacent rearward portions of the longitudinalbearer. The longitudinal bearer comprises a plurality of bearersegments, arranged in succession, and which are connected together atabutting ends or bearing surfaces. The abutting bearing surfaces aredesigned as rotational surfaces in the transverse direction. A central,axially aligned connection is used to join the abutting bearing surfacestogether.

This configuration is especially advantageous when the bearer segmentsare formed as extruded aluminum sections, since the easily accessiblebolt connection permits quick and simple replacement of a forwarddeformed longitudinal bearer piece after a minor collision. Also, thestrength loss problems associated with the replacement of aluminum weldsdoes not occur. However, the costs of such bolt connections arerelatively high.

It is also known from the prior art how to construct a hollow-sectionlongitudinal bearer assembly of a vehicle frame from a plurality ofdeformable longitudinal bearer segments. These individual longitudinalbearer segments are joined together, in end to end fashion, by asurrounding weld beginning with the forward most segment and workingrearwards. Each succeeding longitudinal bearer segment is dimensionedwith a progressingly greater wall thickness and/or are made of aprogressively higher grade of material than its preceding bearer segmentso that the resulting longitudinal bearer assembly has a resistance todeformation which increases toward the middle of the vehicle. Thisprovides for a graduated resistance to deformation up to the middle ofthe vehicle so that in the event of a minor accident, only one or two ofthe forward most longitudinal bearer segments will deform without damageto the adjacent successive (rearward) bearer segments depending on theseverity of the accident. This arrangement greatly facilitates therepair of the vehicle front end since only the deformed segments needreplacement and this arrangement also avoids an undesirable totaldeformation of the vehicle frame in less severe accidents.

In the vehicle frame of the type described, replacement of the deformedlongitudinal bearer segments involved is accomplished by cutting out thedamaged segments and welding on new bearer segments. For the case wherethe longitudinal bearer comprises of sheetmetal segments, this repairprocedure does not give rise to any major structural problems since theoriginal strength of the sheet metal is substantially retained evenafter welding.

It is also well known in the art to provide a connection for alongitudinal bearer in a vehicle body wherein an aluminum bearer isformed as an extruded section and is inserted into a tubular aluminumrecess of a cast metal piece. The aluminum bearer is then welded to thefront edge of this tubular recess by a surrounding weld seam. Such aconnection is stable and economical.

However, it is commonly known that the thermal welding of heat treatablealuminum alloys produces a significant decrease in the strength in thematerial in the so-called "zone of thermal influence" immediatelyadjacent the weld zone. A surrounding weld connection, as is used in theabove-described bearer joint, is especially critical, since it producesa weakening in a continuous transverse plane. The decrease in strengthof a first bearer joint and a first welding procedure can be factoredinto the dimensions. However, in view of the related welding procedurerequired in the typical replacement of bearers whereby the weld seam isfirst cut out and a new bearer piece is then inserted and welded to thefront edge of the tubular recess, there is a resulting uncontrollabledamage to the grain texture and a correspondingly large decrease instrength in the material and danger of fracture during heavy loadconditions.

This is particularly problematic in the situation where the member isconnected to a divided longitudinal bearer, since in this situation itis taken for granted that the more easily deformed forward sections ofthe longitudinal bearer assembly will necessarily be replaced duringrepairs after an accident, and perhaps may even need to be replaced atleast once for normal wear or fatigue during the lifetime of thevehicle. The welding procedures repeatedly required in this case wouldunacceptably weaken the joint by progressive structural change in thezone of thermal influence of the material of the aluminum alloy.

While it is conceivable to incorporate an acceptable safety factor inthe initial design such that the joint is sufficiently thick in thefirst instance so that even the aforesaid severe decrease in strengthcaused by successive welding procedures does not result in danger offracture, this is not a practical solution for reasons of cost andweight. Furthermore, it is desirable to provide the customer with avehicle body which retains its the original strength even after repairs.

SUMMARY OF THE INVENTION

It is a principle object of the present invention to provide an improvedaluminum longitudinal bearer in a vehicle frame comprising a pluralityof bearer segments, each of which are welded together at adjoining ends,and a repair technique for replacing deformed bearer segments whereinthe original strength of the bearer joint is maintained even afterrepair.

It is another object of the present invention to provide an aluminumbearer and repair technique of the type herein described which is of lowcost and which is easy to implement in the conventional vehicle bodydesigns constructed from extruded aluminum frame components.

The invention comprises a method and apparatus for the replacement of adamaged aluminum bearer in a bearer joint of a motor vehicle bodyworkcomprises of aluminum frame members and cast aluminum connectingelements. According to a preferred embodiment of the invention, thefront bearer joint comprises a cast aluminum connector for joining afirst forward most extruded aluminum bearer member to a second adjacentaluminum bearer member which, in turn, is connected to successive bearermembers of the front portion of the motor vehicle body framework inaccordance with the known way. The connector includes a first tubularrecess for receiving the rearward most end of the first forward or frontbearer member. After insertion within the recess, the bearer member isfixed thereto by a peripheral transverse weld disposed at the forwardedge of the recess. The insertion depth of the recess of the aluminumconnector is sufficiently long to allow for two and, preferably, threezones of thermal influence (i.e., the area of the recessed wallimmediately adjacent the transverse weld connection which is thermallyweakened by welding) so that in the event of a collision causing damageto the front bearer member, it can be removed from the recess byperforming a ring cut to the recessed wall at a distance correspondingto the first zone of thermal influence. In this manner, the damagedfront bearer member may be removed from the recess of the connector andreplaced by a new front bearer member which is then welded to the recessat its new forward cut edge.

When appropriately dimensioned the bearer replacement proceduredescribed above may be performed several times without compromise to theoriginal strength of the bearer joint. The repair in this manner alsoeliminates the need for replacing the cast aluminum connectorelement(s). This is desirable since these connectors often serve as anode point for joining together several frame members.

According to another aspect of the invention, transverse marks areprovided to the outer surface of the recess at a distance correspondingto the first, second, third,..., etc., zones of thermal influence. Inthis way, the actual lengths of theses zones of thermal influence aremade visible to the repair worker thereby eliminating guesswork whendetermining the appropriate location for performing the ring cut on therecess wall.

Other and further objects will become evident from the following writtendescription, drawings and claims appended hereto.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partial schematic view in side elevation of the front regionof a vehicle showing the front bearer structure of a vehicle body with atwo-part front longitudinal bearer.

FIG. 2 is an enlarged fragmentary cross sectional view of thelongitudinal bearer joint 3 of FIG. 1 showing the connection of a firstfront longitudinal bearer segment to a second front longitudinalsection.

DETAILED DESCRIPTION OF THE BEST MODE

The following detailed description illustrate the invention by ways ofexample, not by way of limitation of the principles of the invention.This description will clearly enable one skilled in the art to make anduse the invention, and describes several embodiments, adaptations,variations, alternatives and use of the invention, including what wepresently believe is the best mode of carrying out the invention.

FIG. 1 is a schematic cross section view of a vehicle 1 which shows inside elevation view the front region of the bearer structure of thevehicle body generally designated at reference numeral 2. The bearerstructure 2 includes a front longitudinal bearer 3 which consists of aplurality of abutting end-to-end connected light metal structuralmembers, preferably of aluminum alloy, including a first or forwardmostfront longitudinal bearer member 4, an adjacent second longitudinalbearer member 5, a side deviation 6 extending from the rear end ofbearer member 5 to the base of the front door pillar or post 8 and abottom sill 9 which connects to the rearward end of the side deviation6.

The first longitudinal bearer member 4 and the second longitudinalbearer member 5 are joined together by a cast metal piece 15 whichincludes a bottom recess portion 16 for the fitted insertion of thefirst longitudinal bearer member 4. The cast piece 15 also is preferablyformed with an attachment fitting along its upper surface for connectionto the shock absorber strut 10.

A bearer 10 for supporting a shock absorber 11 extends upward from thefront end of the second longitudinal bearer member 5, and is braced byanother, substantially upright bearer 12 which extends upwardly from theright or rear portion of the second longitudinal bearer member 5. Abearer 13 connects the upright bearer 12 to the middle region 14 of thedoor post 8 to complete the front region of the bearer assembly 2 asshown.

FIG. 2 is an enlarged section view through the cast piece 15 shownhaving the first bearer member 4 inserted therein. In the preferredembodiment, the bearer member 4 is cylindrical in cross section, and issized for snug fit engagement within the corresponding cylindricalrecess 16 of the cast piece 15. The cylindrical recess 16 has an overalllength 26. After the first bearer member 4 is secured to the cast piece15 by welding a surrounding transverse weld seam 17 at the front edge ofthe cylindrical recess 16.

In the preferred embodiment, all of the bearer members are extruded orcast aluminum alloy sections. As will be appreciated by those of skillin the art, the welding procedure for the weld seam 17 creates a firstzone of thermal influence 18, wherein a substantial loss of strengthoccurs as a result of structural change in the material. The axiallength of this zone of thermal influence in the material of the recess16 is indicated as zone 18. The first front longitudinal bearer member 4is fashioned as a deformation element so that only this piece willdeform in the event of a minor impact such that the parts comingthereafter, especially the cast piece 15 and the second longitudinalbearer member 5 will not be damaged. In such an impact, only the frontlongitudinal bearer member 4 needs to be replaced.

In accordance with the method aspects of the invention, the first stepof the repair involves cutting off an outer ring portion 19 of therecess 16 at line 20 which corresponds to a safe distance beyond theweakened first zone of thermal influence 18. The ring portion 19including the aluminum bearer 4 connected thereto by the weld seam 17 isthen removed from the recess 16. Next, a new longitudinal bearer member4 is inserted within the recess 16 (the depth of which is now shortenedby a distance corresponding to the first zone of thermal influence 18)and welded to the recess by a new weld seam at 21, thus forming a secondzone of thermal influence 22.

If another impact occurs which again results in the deformation of thefirst longitudinal bearer member 4, the above-described procedural stepsmay be repeated to perform another repair. That is, the second zone ofthermal influence 22 is cut away and a new longitudinal bearer piece 4is again attached by a weld seam at 23. The depth dimension of theremaining insertion zone 24 is selected to be sufficiently long toprovide a strong and positive-locking connection. Notches or similarmarking may be provided at the proposed seams 21 and 23 to assist theworker in making the repair.

This provides a repair procedure for bearers which are originallyfastened by welded connections can be replaced and again fastened withanother welded connection a number of times, without sacrificingstrength.

It should be understood that various modifications within the scope ofthis invention can be made by one of ordinary skill in the art withoutdeparting from the spirit thereof. For example, while the invention hasbeen described in detail with particular reference to the repair ofdamaged front longitudinal bearer members only, it is understood thatthe teaching principles of the invention may also be applied to aluminumbearer members located in other portions of the vehicle bodywork andwhich are subject to buckling along a common longitudinal axis. Wetherefore wish our invention to be defined by the scope of the appendedclaims as broadly as the prior art will permit, and in view of thespecification if need be.

We claim:
 1. A longitudinal front bearer joint assembly in a motorvehicle bodywork comprising in operative combination:a) a first aluminumbearer member; b) a second aluminum bearer member disposed behind saidfirst aluminum bearer; c) a cast aluminum connector for joining saidfirst aluminum bearer member to said second aluminum bearer member, saidconnector having:i) a first connector end mounted to a front end portionof said second aluminum bearer member; ii) a connector portion having atubular recess for receivingly engaging a rear end portion of said firstaluminum bearer member and terminating in a forward perimeter edge; d)said connector is secured to said first bearer member by a weld seamdisposed at said forward perimeter edge of said connector portion; e)said connector portion having an axial depth dimension which includes:i)a locking length segment defining a minimum depth sufficient to ensure apositive locking engagement of said connector with said first aluminumbearer member; ii) at least one thermal length segment corresponding toa zone of thermal influence wherein a significant decrease in strengthof the bearer joint occurs as a result of said weld seam; and f) atleast one transverse marking disposed along an outer surface of saidconnector portion at a point corresponding to a boundary location forsaid at least one thermal length segment.
 2. A longitudinal bearer jointas in claim 1, wherein said axial depth dimension of said connectorportion includes at least one additional thermal length segment arrangedadjacent said at least one thermal length segment.
 3. A longitudinalbearer joint as in claim 2, which includes at least one additionaltransverse marking disposed along an outer surface of said connectorportion at a point corresponding to a boundary location for said atleast one additional thermal length segment.
 4. A method of replacementof said first aluminum bearer member in the longitudinal bearer joint ofa motor vehicle bodywork of claim 1 comprising the steps of:a) making acut to remove a forward ring portion of said connector portion, said cutbeing located behind said perimeter edge weld seam at a distancecorresponding to said at least one thermal length segment and forming anewly cut perimeter edge of said connector portion; b) removing saidfirst aluminum bearer member including the cut ring portion weldedthereto; c) inserting a replacement first aluminum bearer member withinthe remaining connector portion; and d) welding said replacement firstaluminum bearer member to said newly cut perimeter edge of saidconnector portion.
 5. A method for replacement of an aluminum bearer asin claim 4, wherein said axial depth dimension of said connector portionincludes at least one additional thermal length segment arrangedadjacent said at least one thermal length segment.
 6. A method forreplacement of an aluminum bearer member as in claim 5, which furtherincludes marking the outer surface of said connector portion with atleast one cut point corresponding to a boundary location of said atleast one additional thermal length segment.